Natural Virus Said to Check Brown Tide

A discovery by scientists may help Long Island fishermen who have been plagued for nearly a decade by brown tide, a mysterious, troublesome algae growth that turns sea water the color of coffee and chokes the life out of waterways where shellfish once thrived.

The scientists report that they have isolated a number of viruses that live in the sea water and can destroy the microscopic brown tide algae. While the results are preliminary, the scientists say the discovery may lead to the use of the viruses to help prevent the spread of brown tide.

The viruses were isolated by Dr. Elizabeth M. Cosper and Kristen L. Drewes Milligan at the State University of New York at Stony Brook. In a paper to be published Friday in the journal Science, they report they isolated the viruses by filtering them from water samples taken in 1992 from the Great South Bay and West Neck Bay, two Long Island bays that were hard hit that year by brown tide.

Dr. Cosper said in an interview that the filtered material was added to cultures containing the brown tide algae. Time after time, she said, the algae was destroyed. That has led her to hypothesize that the virus -- which normally exists in nature with the algae and may control its growth -- might be applied to halt blooms of brown tide.

"If we know what's happening, then we have the knowledge to perhaps control the blooms," said Dr. Cosper, a marine biologist and professor at Stony Brook. "If you know you can spray out a certain virus, if you know you have something that can kill off an organism that can kill off a shell fishery, I think people would want to test that out."

Brown tide was first observed in 1985 on Narragansett Bay in Rhode Island, and in the Peconic and Great South Bays of Long Island. The rapid algae growth turned the water deep brown, blocking out light and causing the widespread destruction of eelgrass on the bottom. The algae wiped out vast populations of bay scallops, once the mainstay of a thriving shellfish industry on Long Island's East End.

Mysteriously, while the brown tide disappeared from Narragansett, it reappeared again and again in Long Island waters, confounding scientists trying to determine the cause of the blooms and the site of their next infestation. Dr. Robert Nuzzi, a marine biologist and supervisor of the Bureau of Marine Resources for the Suffolk County Department of Health Services, said the outbreaks remain such a puzzle that a mathematician was recently consulted to try to discern some statistical pattern to the blooms.

Dr. Nuzzi said that while it is conceivable the viruses could be used to wipe out the blooms, the Stony Brook work brings him no closer to what he considers the ultimate question: What causes the blooms? "It can tell us why the bloom dies off, why it crashes," he said. "But it's not necessarily telling us why the bloom occurs to begin with."

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There are various theories about what environmental conditions contribute to the blooms, including salinity of the sea water, and the types of human and manufactured waste that runs off land and into waterways. Dr. Cosper said that the interaction between the viruses and the algae, which go by the scientific name Aureococcus anophagefferens, may also play a part: it may be that when for some reason the natural balance between them is off, the algae grow uncontrollably.

Even less is understood, however, about artificially introducing viruses into the ocean. Bacteria and other biological agents have been used to control all kinds of pests and problems, from insects to oil spills. But the study of how viruses behave in the oceans is so new that experts can only guess at how long it will take to grasp the environmental consequences of unleashing viruses into the oceans. It is only in the last few years that marine biologists have begun to learn about the vast number and variety of viruses in the seas.

"We're just beginning to scratch the surface in trying to understand how viruses interact in the marine system," said Curtis Suttle, a professor at the University of Texas's Marine Science Institute who is also isolating viruses in microscopic marine life, like phytoplankton. "There are about 100 million viruses in every teaspoonful of sea water."

John McN. Sieburth, professor emeritus of oceanography at the University of Rhode Island and co-discoverer of anophagefferens, called the Stony Brook work "a big step" in understanding subtleties in the relationship between virus and algae. "What this will allow Cosper and others to do is try different concentrations, and find out at what populations the virus takes over," he said. That, in turn, would lead to an understanding of how to assert "viral control" over a bloom.

Although there was a brief brown tide bloom on the Great South Bay last summer, there have been no prolonged outbreaks of brown tide since the large blooms of two years ago. As a result, the bay scallop is making something of a comeback on the East End. This year, marine biologists say, the scallops are more abundant than any time since the emergence of brown tide.

But that could change quickly, if the brown tide returned. "It's a very scary thing," Dr. Nuzzi said. "We don't know what triggers it."

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A version of this article appears in print on November 4, 1994, on Page B00001 of the National edition with the headline: Natural Virus Said to Check Brown Tide. Order Reprints|Today's Paper|Subscribe